Mentor:  Dr. Margaret Johnson, Assistant Professor, Department of Chemistry, University of Alabama at Birmingham, CHEM 274, 1720 2nd Avenue South, Birmingham, AL 35294-1240. Telephone:  (205) 934-8137 Fax: (205) 934-2543

A Postdoctoral fellowship is available at the University of Alabama at Birmingham in the laboratory of Dr. Margaret Johnson. We use solution NMR spectroscopy and other biophysical techniques to investigate the structure and function of proteins involved in the metabolism and molecular recognition of poly(ADP-ribose), a key biomolecule in the maintenance of genome integrity, chromatin structure, and the cell cycle. Areas of research include determining high-resolution structures of proteins and protein complexes, enzymatic synthesis and computational simulations.

Our laboratory is part of the Comprehensive Cancer Center and Center for Structural Biology at UAB. The Central Alabama High-Field NMR Facility is equipped with Bruker 850, 700, 600 and 500 MHz spectrometers with TCI cryoprobes. Biophysics facilities include MALDI-TOF mass spectrometry, fluorescence spectroscopy, analytical ultracentrifugation, titration calorimetry, high-throughput screening and protein crystallization, and high-performance computing.

UAB is the top university and 8th overall institution in the Best Places to Work (Postdocs) survey published in The Scientist (2013). The campus is a major part of the downtown landscape, and is within walking distance of some of the best parks, entertainment and dining in the region. We offer high-quality training and mentoring, pay and benefits, career development, networking, and opportunities for family and personal life. The Office of Postdoctoral Education offers classes in grant writing, laboratory management, research ethics, and teaching and presentation skills. Interdisciplinary research seminars are ongoing in a variety of university-wide interest groups.

Enthusiastic, motivated researchers are encouraged to apply. Candidates should have recently received a Ph.D. in a related discipline and have a strong background in structural biology or biochemistry. To apply please send a cover letter, CV, and contact information for three references to Dr. Margaret Johnson at maggiejohnson@uab.edu. UAB is an equal opportunity/affirmative action employer.

  

Postdocs in UAB News

  • A novel toxin – and the first ever found – for a deadly pathogen, M. tuberculosis
    Until now, no toxin had been found in 132 years of study for the deadly pathogen Mycobacterium tuberculosis, which infects 9 million people a year and kills more than 1 million. The novel toxin induces necrotic cell death of macrophages to help the tuberculosis pathogen escape and spread to other cells.

    Despite 132 years of study, no toxin had ever been found for the deadly pathogen Mycobacterium tuberculosis, which infects 9 million people a year and kills more than 1 million.

    Now, Michael Niederweis, Ph.D., professor of microbiology at the University of Alabama at Birmingham, and colleagues have described the first known toxin of this pathogenic bacterium. This toxin — Tuberculosis Necrotizing Toxin, or TNT — is the founding member of a novel class of previously unrecognized toxins present in more than 600 bacterial and fungal species, as determined by protein sequence similarity. Before the Niederweis discovery, those toxins were identified only as the “Domain of Unknown Function 4237.”

    Bacteria with those newly recognized toxins include Yersinia pestis, the pathogen that caused the bubonic plague known as the Black Death in Medieval Europe, and Listeria monocytogenes, one of the most virulent and deadly food-borne infections and the cause of Blue Bell Creameries recalls this year.

    The lack of an identified toxin in M. tuberculosis had contrasted with nearly all other pathogenic bacteria whose toxins contribute to illness or death.

    M. tuberculosis is notable for its survival inside macrophages, the immune cells that ingest and destroy infectious bacteria. The newly identified TNT, Niederweis says, plays a key role to induce necrotic death of the infected macrophage. Thus, TNT enables the M. tuberculosis bacteria to escape from the macrophage and disseminate to other host cells in a person infected with tuberculosis, thus contributing to the survival of M. tuberculosis and spreading the disease.

    “The battle between M. tuberculosis and the human immune system to control the fate of infected macrophages is critical in determining the outcome of the infection,” Niederweis wrote in the TNT paper. “The control of host cell death is of utmost importance for the survival, escape and dissemination of M. tuberculosis.”

    The paper, “The tuberculosis necrotizing toxin kills macrophages by hydrolyzing NAD,” was published online Aug. 3 in Nature Structural & Molecular Biology.

    How did this toxin evade discovery for more than a century? First, it is produced in vitro only in very small quantities — the Niederweis lab could detect it only in a cell culture filtrate that was concentrated 1,000-fold, equivalent to concentrating a gallon of milk to about one-third of a teaspoon. Second, the toxin is deadly only when it is inside the host-cell cytosol; if the toxin is in the bloodstream or is added to the culture medium of in vitro host cells, it has no effect. Third, the toxin has no similarities to any other known toxin.

    Niederweis discovered TNT while searching for something completely different. He was hunting for outer-membrane proteins that can act as a door to let nutrients outside the bacteria pass through the extremely impermeable, outer-membrane barrier of M. tuberculosis. The Niederweis group thought they had found such a porin protein; but it had an unusual property — the end portion of the protein broke off after the pore formed in the outer membrane, and that end portion was extremely toxic, both in simple prokaryotic cells like bacteria and in the more complex eukaryotic cells of yeast, mammals and fish. In a paper published in Proceedings of the National Academy of Sciences in 2014, Niederweis said this discovery “challenges the paradigm that M. tuberculosis is one of few bacterial pathogens that does not produce toxins.”

    In this illustration, the Tuberculosis Necrotizing Toxin — symbolized by the explosives — has caused necrotic cell death and release of the tuberculosis bacteria from the macrophage. Credit: Mathew Schwartz (Advanced Institutes of Convergence Technology, SNU)The current paper fully establishes this new paradigm by identifying the mechanism of TNT-induced necrotic cell death at the functional and structural levels. Like an optical illusion where at first one sees a vase, and it then appears to be two faces peering at each other, Niederweis initially he believed he had found an outer-membrane porin that lets nutrients in and carried an artefact. Now he sees the pore part of that protein as a bacterial autotransporter (similar to those seen in other bacteria) that exports its TNT protein cargo to the outside of the outer membrane. After that export is done, the transporter pore remains in the outer membrane.

    The similarity of the tnt gene to DNA sequences in more than 600 other bacterial and fungal species will enable research on how this novel class of toxins may function in other pathogens, especially in microorganisms that depend on induction of necrosis to survive or spread.

    Here are some details of TNT:

    1. In a laborious search for the molecular function of TNT, Jim Sun, Ph.D., a postdoc in the Niederweis lab, found that TNT hydrolyzes the essential co-enzyme nicotinamide adenine dinucleotide (NAD+). This explains why it kills every type of cell it is cloned into, because NAD+ is necessary for the cell’s normal metabolism. Researchers were able to clone the TNT gene only by placing it next to an inducible promoter that tightly represses transcription until induced. The TNT enzyme hydrolyzes NAD+ inside of cells and in vitro. It is blocked by antibodies against TNT, and specific TNT point mutations that eliminate all enzymatic activity.
    2. That noncatalytic TNT mutant is not able to kill macrophages, showing that the hydrolase activity is required for TNT-induced cell death.
    3. If TNT were produced inside M. tuberculosis, it would kill the cell. Niederweis and colleagues found that M. tuberculosis, similar to the bacterial pathogen Streptococcus pyogenes, produces an antitoxin to its toxin. The TNT antitoxin binds to the toxin and blocks its hydrolase activity, thus making it harmless inside the bacteria. The researchers have named the antitoxin immunity factor for TNT (IFT).
    4. Cloning the genes for both TNT and IFT into E. coli, where IFT protects the bacteria from death, allowed the researchers to produce milligram quantities of TNT and IFT. In a collaborative effort, Gino Cingolani, Ph.D., a professor from the Thomas Jefferson University, produced crystals of the purified protein complex and determined its molecular structure to an astonishing resolution of 1.1 Å in a matter of weeks. The TNT molecule is shaped like a grasping hand, with fingers on one side and an extended thumb on the other. The IFT fits into the TNT like a ball held in a hand.
    5. When pathogenic M. tuberculosis grows inside a macrophage phagosome, the TNT rapidly gains access to the cytosol of the infected macrophage and hydrolyzes NAD+, depleting that essential co-factor. This initiates necrotic cell death through downstream signals that are not yet characterized.

    Curiously, a literature search revealed that an uncharacterized, heat-stable NAD+-glycohydrolase activity in M. tuberculosis cell extracts had been described half a century ago, as well as an uncharacterized heat-labile inhibitor of that hydrolase activity. Several biochemical characteristics of TNT and IFT found by the Niederweis lab match those of the uncharacterized proteins described in the reports from the 1960s.

    However, the lack of the modern equipment and antibodies of today, and the very low levels of TNT present in M. tuberculosis, prevented those researchers from finding the toxin.

    Co-authors of the paper are Jim Sun, Ph.D., Axel Siroy, Ph.D., Alexander Speer, Ph.D., and Kathryn Doornbos, all in the Department of Microbiology, UAB School of Medicine; and Ravi Lokareddy, Ph.D., and Gino Cingolani, Ph.D., Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia. Siroy is now at the University of Maastricht, the Netherlands.

  • Floyd named president-elect of National Neurotrauma Society

    UAB’s Candace Floyd is set to take a top leadership post with the National Neurotrauma Society.

    Candace Floyd, Ph.D., associate professor in the University of Alabama at BirminghamDepartment of Physical Medicine and Rehabilitation, is the president-elect of the National Neurotrauma Society. The president-elect will assume the duties of president in June 2016 for a one-year term. Floyd previously served terms as vice president and secretary/treasurer.

    The National Neurotrauma Society seeks to accelerate research that will provide answers for clinicians and ultimately improve the treatments available to patients. It is open to scientists interested in neurotrauma research and promotes excellence in the field by providing opportunities for scientists, establishing standards in both basic and clinical research, encouraging and supporting research, and promoting liaisons with other organizations that influence the care and cure of neurotrauma victims.

    Floyd is the holder of the Women’s Committee of Spain Rehabilitation Center Endowed Chair in Rehabilitation Neuroscience Research and the director of Research for the Department of Physical Medicine and Rehabilitation. The central focus of her research is to develop new treatments for spinal cord injury and traumatic brain injury.

    She earned her doctorate from the Medical College of Virginia/Virginia Commonwealth University and did postdoctoral training in traumatic central nervous system injury research at the University of California, Davis. She joined UAB in 2006.

    She serves as grant reviewer for the National Institutes of Health, the Department of Defense and the Department of Veterans Affairs. Her research is currently supported by the Department of Defense, the National Institutes of Health and private organizations including the National Football League.

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UAB Research News

  • UAB students use performance, interactivity and alternative materials to create art for one-night-only exhibition Aug. 5
    Sculptural objects, masks, puppets, performances and art installations created by Department of Art and Art History students will be shown in a one-night-only exhibition.

    Sculptural objects, masks, puppets, performances and art installations will be shown in a one-night-only exhibition Wednesday, August 5, presented by the University of Alabama at BirminghamCollege of Arts and SciencesDepartment of Art and Art History.

    Two one-night-only exhibitions will be presented from 6-8 p.m. Students in Assistant Professor of Sculpture Stacey Holloway’s summer interdisciplinary Interlude: Space & Body course engaged in projects that consider the role of performance and interactivity within contemporary art making. Works by each student can be seen in the exhibition in the Department of Art and Art History Project Space, on the first floor of the Humanities Building, 900 13th St. South.  

    “In this course, students focused on three main projects: relationships between audience and sculptural objects; creating narratives through objects and performance; and puppetry and set design,” Holloway said. After researching contemporary artists who use their own bodies in interactive and performance art practice, such as Janine Antoni, Joseph Beuys, Felix Gonzalez-Torres, Basil Twist and Tomás Saraceno, the students experimented with 3-D sketches, audience interaction and performance while working with nontraditional materials. 

    “Through the investigation of mixed media, including but not limited to drawing, sculpture, photography, video and installation, students explored the possibilities that occur when the body, space and the art object merge,” Holloway said. 

    The students are Tori Absher, Corey Bright, Hannah Hensley, Keila Kirkwood, Bryce Martinez, Jenifer Moore, Lisa Nguyen, Jennifer Rice, Caelum Soverow, Adam Sterrett, Annie Strong and Kylee Williams.

    Also presented Aug. 6 from 6-8 p.m., students from Adjunct Professor Lane Cooper’s summer figure drawing course will open “The Eccentric Nine” in the UAB Painting Studio, located on the third floor of the Humanities Building. Students who will have works featured are Amanda Halbrooks, Marlena Roberts, Augusta McKewen, Ashlee Boren, Ellory Nichols, Jack Vest, Ricardo Munoz, Corey Bright, and Chris Golson.

    The Department of Art and Art History’s Project Space is an adaptive space that cultivates and supports meaningful creative investigation, interdisciplinary collaboration, innovation and entrepreneurship by providing an alternative platform for students, faculty and community to engage teaching, research, public service and visual art practices.

    “Throughout the summer, students were introduced to formal figurative drawing and challenged to consider the figure in contemporary art practice,” says Cooper, “while the second half of the semester involved working with ideas, themes, texts and practical concerns of figurative themes.”

    The Department of Art and Art History’s Project Space is an adaptive space that cultivates and supports meaningful creative investigation, interdisciplinary collaboration, innovation and entrepreneurship by providing an alternative platform for UAB Department of Art and Art History students, faculty and community to engage teaching, research, public service and visual art practices.

    For more information, contact Assistant Professor of Sculpture Stacey Holloway at shollow@uab.edu.

  • Most Obstetricians Screen for Group B Strep at 35 to 37 Weeks
    Almost all obstetricians collect group B streptococcus screening samples, but practice patterns vary, according to research published in the August issue of the American Journal of Obstetrics & Gynecology.
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